Deciding to implement a gantry system or robot for your manufacturing application is not as straightforward as it might seem. To automate a simple but time-consuming and potentially dangerous task on its factory floor, a chipboard company weighed up the benefits of a gantry-actuator system against those offered by a robotic system.
Robot or Gantry?
Chicago Electric was approached to design an automation system for stacking metal screens used to make chipboard. These screens are stacked at the end of the process and sent back to the beginning of the line for reuse in the next cycle. The manual process involved two workers, placed on opposite sides of the line. The low added value of the task on which the two operators were employed prompted the company to optimize the process by introducing automation.
“After considering important factors such as cost and efficiency, we chose a gantry system instead of a robot,” said Bob Kaska of Chicago Electric.
Using a gantry requires less maintenance than maintaining a robot, as it uses only two motors instead of six. The application also provides greater ranges and capabilities than a robot can offer. In addition, the range of motion required and the weight of the product being handled would have made robotic implementation at least twice as expensive as the gantry solution.
Chicago Electric designed an X-Z gantry system for stacking metal screens built around a pair of coupled Rollon actuators. Task automation has made it possible to deploy operators to higher value tasks, improving ergonomics and phase efficiency.
“The decision to go down an automation path was driven primarily by the need to make the application more secure,” Kaska said.
“The task involved repetitive movements and coordination of two people. In order to place the screen on the moving belt, it was necessary for the operators to be in close proximity to the equipment: this exposed them to potential hazards.”
Rollon Linear Actuators, a reliable solution
The biggest difficulty in developing the application was finding an actuator that met all the requirements of the application. The elements to consider when selecting an actuator are accuracy, repeatability, capacity and stroke length. For this gantry system, Chicago Electric chose Rollon’s R-SMART 160 and SC-130 linear actuators. With a carriage made of fabricated anodized aluminum, the R-SMART 160 uses a dual linear rail, rather than a single one, to provide higher load capacity at higher moments and properly handle the amount of weight required.
The SC-130, part of Rollon’s PLUS series, mounts directly to the R-SMART unit without an adapter plate. This actuator also features high capacity and increased rigidity. Another important feature of the SC-130 is its stationary carriage and mobile extrusion. This feature makes the actuator a good choice for applications.
Cycle time reduction
The X-Z gantry system designed by Chicago Electric is a pick-and-place system that reduces cycle time from 30 to 15 seconds while improving safety. This fully automated pick-and-place system travels 3.7m horizontally and 1.2m vertically to stack metal screens. The X-axis of the system has a velocity of 1.3 m/s and a force of 270 kg. Its Z-axis has a stroke of 122 cm and a force of 224 kg. Also on the Z-axis, the gantry features a heavy-duty magnetic tool that tilts when the tool drops. Chicago Electric’s pick-and-place system also features a 1.27-inch header bar that is engaged by a chain conveyor and used to connect the steel screens.
Extended system life
Rollon engineers determined that the Z-axis moment on R-SMART would be the limiting factor in this X-Z gantry system. With a maximum velocity of 1.5 m/s, an acceleration of 33 g, and a 1/3 safety factor, this actuator has an Mz of 1192 Nm, which is well within the 5707 Nm limit. Rollon performed a calculation of the solution’s longevity estimating it at 21 years.
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